• Morishita16_Fig5

    GLASS Reveals Dual-Role Environments in Galaxy Clusters

    Using the GLASS spectroscopic and very deep imaging data, Morishita et al. (2016) found that galaxy clusters are dual-role environments, which both accelerate and curtail galaxy evolution without affecting their sizes and structures. Morishita et al. derived structural parameters of more than 3900 galaxies by using the GLASS grism spectroscopy combined  with the imaging from the Hubble Frontier Fields.… Continue reading →

  • MACS0416lensfig

    MACS0416 lens model and surface mass density map from GLASS spectroscopy

    In Hoag et al. (2016), the GLASS team used the GLASS spectroscopy combined with the deep imaging from the Hubble Frontier Fields (HFF) to produce a gravitational lens model of the galaxy cluster MACSJ0416.1-2403 (MACS0416), following the approach by Wang et al. (2015) who modeled Abell 2744. The GLASS data allowed the team to measure… Continue reading →

  • winter16clusters

    Completion of GLASS NIR data release v001

    With the release of the NIR data products and redshift catalogs for the clusters A370, MACS0416, MACS0744, the GLASS NIR v001 data release is now complete! All data products including individually extracted grism spectra in 1D and 2D as well as redshift catalogs for all 10 GLASS clusters are available on the GLASS MAST webpage:… Continue reading →

  • samplehistogram_stacked_EL

    GLASS presents 24 potential Lyα emitters at z ≥ 7

    In the most recent paper by the GLASS collaboration, Schmidt et al. (2015), we present a sample of 24 objects with emission lines consistent with being Lyα at redshifts around or above 7, at the heart of the epoch of reionization. The figure shows the redshift distribution of these line emitters. Taking advantage of the… Continue reading →

  • Halpha_map

    The Spatial Extent of Hα in Cluster Galaxies from GLASS Pilot Study

    The GLASS data yield spatially resolved Hα fluxes for all star-forming galaxies in the core (< 1 Mpc) of the clusters. In addition, each cluster is observed at two different position angles. These two orientations allow us to mitigate the impact of contamination from overlapping spectra, and reliably measure for the first time the relative… Continue reading →

  • GLASS_M0717specz

    GLASS Survey Paper and First Data Release

    Today we released the GLASS survey paper together with the first data product of the survey. The paper gives a thorough overview of GLASS and its science goals. We utilize the Hubble Frontier Field cluster MACSJ0717, the first cluster to be observed by GLASS, to illustrate the data quality and the high-level data products we… Continue reading →


GLASS is a cycle-21 large program with the Hubble Space Telescope, targeting 10 massive clusters, including the 6 Frontier Fields, using the WFC3 and ACS grisms. The program consists of 140 primary orbits (with the G102 and G141 grisms) and 140 parallel orbits (with the G800L grism). Using the clusters as cosmic telescopes, GLASS is taking spectra of faint background galaxies with unprecedented sensitivity and angular resolution. GLASS has three primary science drivers, although a variety of other science investigations are possible in combination with existing and planned imaging campaigns like the Frontier Fields Initiative and CLASH .

The key science drivers of GLASS are:

- To shed light upon the role of galaxies in reionizing the universe, the topology of high redshift intergalactic/interstellar medium and on Lyman alpha escape fraction.
- To study gas accretion, star formation and outflows by mapping spatially resolved star formation and metallicity gradients in galaxies at z = 1.3 - 2.3.
- To study the environmental dependence of galaxy evolution, by mapping spatially resolved star formation in galaxies in the cluster cores and infalling regions.


The survey strategy, science drivers, released data products and software tools are all described in the GLASS survey paper Treu et al. (2015)

If you find any of the GLASS products useful, please cite: